1. Field of the Invention
This invention relates to packaging electronics assemblies to withstand external loads such as shock, vibration or temperature cycling. These external loads deflect the printed circuit boards (PCBs) or heavier electronic components stressing the solder connections causing them to weaken or break.
2. Description of the Related Art
An electronic assembly includes electronic components that are mounted on the surface of a printed circuit board (PCB) and electrically connected via solder connections. The electronic components may include all types of surface mount and through-holes components or integrated circuit (IC) chips. The PCB is a non-conductive substrate that provides a mechanical carrier to support the layout of the electronic components. The electronic components and solder connections may be mounted on either or both sides of the PCB.
In certain products and applications, electronic assemblies must withstand and operate in extremely challenging environments including but not limited to random transport vibration, extreme shock from explosions, dropping etc. and extreme temperature cycling over a multi-year product life. These externals loads cause the PCB to flex and apply high forces to heavier components. This in turn stresses the solder connections causing them to weaken or break.
The electronic assemblies may be “encapsulated” to mitigate the effects of these external loads. In a typical process, a stack of electronic assemblies are assembled to a lid using rigid standoffs and bolts. The stack is then inserted into a housing and the lid is secured. The lid and other through-housing connectors are sealed. Encapsulant material is injected into the housing and cured so that it bonds to the PCBs and electronic components. As the potting material is cured “in-situ” it forms a matched pair to each electronic assembly that absorbs any variations in geometry due to manufacturing tolerances. The cured material supports the PCBs and electronic components to minimize deflection and the resulting stress on the solder connections in response to external loading.